I'm not much of an AC fan. I liked 1 and the 2 trilogy but was bored with 3 and 4 and then I stopped playing the series entirely because it all seemed like the same tired formula. The thing that I didn't like the most about the AC series was that, if you were eventually seen, the open combat really, really sucked, mostly consisting of waiting for an enemy to attack and then countering. Origins really peaked my interest with its completely revamped, action RPG game play, and I really enjoyed it! It also helped that Bayek and Aya were interesting characters to me, and I enjoyed the more personal-feeling themes of parenthood and family.
With Odyssey, I'm 33 hours in at level 28 out of 50, and I'm absolutely loving this game! According to the Uplay stats, I am only 26% done the main story, and this is because there is just so much content. Now, much of that content could be considered filler depending on how much you enjoy doing them: random forts; randomly generated kill & fetch quests with throwaway characters and plots that you get from a message board; the faction region control and conquest battles where you fight alongside an army; and the puzzles where you have a clue to guide you to a treasure location. There are, however, plenty of, in my opinion, good-to-excellent "main" side quests spread out across the lands. I would argue that these are often close to the same quality level as The Witcher 3's side quests with a lot of attention to detail (being able to do steps out of sequence or doing something unconventional while having these acknowledged with different outcomes; multi-quest storylines that span multiple regions with unique characters, dialogue, and consequences), but it's hard for me to directly compare them since W3 was generally much more serious in tone while Odyssey is, I feel, more varied with a lot of lighthearted but also really dark moments. I really, really liked The Witcher 3 (180 hours played, bought the collector's edition which wasn't even available in my country of Canada. I should also disclose that I bought the Spartan Edition of Odyssey since it seemed to mimic a lot of what I liked about W3), and this is an informed but premature opinion, but I am actually debating with myself over whether I like Odyssey more than The Witcher 3. I believe that the main and side stories of W3 were better written but the game play of Odyssey is much better with far less inventory management and more responsive and varied combat (I really liked W3's combat, but it's hard to beat the assassination/bow/Spartan-kicking trifecta of Odyssey). If Odyssey keeps this up, it will enter my top 5 games of all time which currently stands as the following: World of Warcraft (played for 6 years), Diablo 3 + expansion (over 3,000 hours played across 3 or 4 years), Metal Gear Solid 5 (118 hours), The Witcher 3 (180 hours), and Saints Row The Third (128 hours). All of those are very game play-focused games with interesting systems and high replay value or just tons of engaging content.
Having said all of that, Odyssey is an action RPG and very different from most entries in the series. If you don't like the concepts of leveling and stats (which includes possibly not successfully one-shot assassinating certain enemies unless you're high enough level with the right gear and specialization) or if you just want to rush the main story without dealing with any side content (of which I'd argue that there's a lot of quality content such that you can mostly avoid doing the boring, repetitive fluff) or you don't like the idea of exploring a vast, lush, colourful open world, then perhaps this game is not for you.